A shaped article is obtained by polymerizing a selectively reflective solution comprising a cellulose derivative and a polymerizable solvent. The cellulose derivative is a cellulose derivative having an alkyl degree of substitution of about 2.2-3, an acyl degree of substitution of about 0-0.8 (preferably 0.1-0.8), and a total degree of alkyl and acyl substitution of about 2.8-3. The cellulose derivative is thus, e.g., a highly substituted alkyl cellulose (ethyl cellylose) or an acylated alkyl cellulose. Moreover, the polymerizable solvent may be a (meth)acrylic monomer (e.g., (meth)acrylic acid). According to the present invention, a shaped article having selective reflectivity with respect to wavelength and circularly polarized light is provided.

New compounds of the spiro-indoline-oxazine class possessing photochromatic and photosensitizing charecteristics are definable by the general formula (I): ##STR1## where the substituents R, R.sup.1 -R.sup.7 and A are as defined in the description. The process for preparing the compounds (I) is described, as is their use as photochromic agents able to confer photochromatic characteristics on the articles in which they are incorporated, and as photosensitizing agents.

A method of treating a surface by laser ablation to modify selected regions of the surface, while other regions of the surface not to be substantially ablated are protected from the laser beam by a masking fluid, wherein the masking fluid comprises a solution of a pharmaceutically acceptable pyrido benzoxazine compound or derivative thereof effective as a masking agent.

Described are novel reversible photochromic spiro(indoline) naphthoxazine compounds of improved photocolorability that may be graphically represented by the formula, ##STR1## In preferred embodiments, R.sub.1 is allyl, alkoxyalkyl, and alkyl; each R.sub.2 is alkyl or alkoxy; R.sub.3 and R.sub.4 are alkyl; R.sub.5 is alkoxycarbonyl; and R.sub.6 is hydroxy, alkoxy, or carboxy, e.g., acetoxy. Also described are organic host materials that contain or that are coated with such compounds. Articles such as ophthalmic lenses or other plastic transparencies that incorporate the naphthoxazine compounds or combination thereof with complementary photochromic compounds, e.g., naphthopyran or benzopyran compounds, are also described.

A device to measure the amount of ultraviolet (UV) light transmitted through a water sample, relative to the amount of UV light transmitted through a sample of known UV transmittance, known as UV percent transmittance (UVT). A single UV sensor is used to measure the amount of UV light transmitted through the blank sample and through the water sample under test. In order to maintain accuracy, compensation must be made for fluctuations or drift in the UV lamp output which is common in UV lamps and due primarily to changes in temperature and imperfections in the lamp. The UV sensor measures the amount of light being emitted by the lamp at the times before and/or after the UV sensor measures the amount of UV light transmitted through the blank and water samples. A microprocessor computes the UVT while using the detector readings to compensate the calculated UVT for any drift and fluctuations in the UV lamp output.